Challenges in Measuring Thin SiO2 Layers on 4H-SiC via Spectroscopic Ellipsometry

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Abstract:

The measurement of thin silicon dioxide (SiO₂) layers on silicon carbide (SiC) substrates is crucial because these layers serve a variety of critical functions in electronic and optoelectronic devices. Silicon carbide’s superior electrical and thermal properties make it a preferred material for high-power, high-frequency, and high-temperature applications. When deposited on SiC, thin SiO₂ films act as preconditioning layers, and as gate oxides, precise measurement of these oxide layers is important to ensure both optimal functionality and extended device longevity. This paper presents the essential considerations that should be addressed when Silicon-Oxide layers on SiC substrate are measured by spectroscopic ellipsometry to avoid backside artifact and enhance sensitivity in their thickness measurements. The methodology demonstrated enables reliable detection of layer thicknesses down to less than 1 nm, with a discrimination of less than ±0.5 nm. During ellipsometry data evaluation, parametric models are applied to describe the anisotropic backside reflections. Incorporating additional parameters, such as the substrate thickness, can yield deeper insights into the sample. However, this added complexity can render the modeling approach impractical for routine industrial applications, even though it remains scientifically valuable. Overall, this study emphasizes the combined importance of using a microspot system and optimizing the incidence angle to overcome the inherent challenges of measuring thin SiO₂ films on 4H-SiC.

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